A printer which prints upon reception of a print job via a network from a host terminal is commonly known as a network printer. In an environment in which a print job is transferred via a network, the integrity of confidential information contained in the print job must be secured. Examples of a general method of securing the integrity of confidential information are as follows.
First, when a print job containing confidential information is to be transmitted to a print node, a host computer encrypts the print job and then transmits it to the print node. The print node decrypts the encrypted print job and prints it (see, e.g., Japanese Patent Laid-Open No. 2004-086894).
Second, a print node temporarily stores a print job transmitted from a host computer, and only when the print node authenticates the user by using an IC card or the like, permits printing (see, e.g., Japanese Patent Laid-Open No. 2001-188664).
As a means for implementing the first method, a printer itself directly comprises a function for decrypting encrypted data. In addition, a control device may be arranged on the input stage of the printer and equipped with a decryption function. In this later case, the printer does not need to include a decryption function, and instead a conventional printer can be advantageously used.
In association with this, Japanese Patent Laid-Open No. 2001-159960 discloses a form in which a printer is connected to a set-top box installed in the subscriber's house or the like in a two-way communication system capable of using the Internet service. This reference discloses a technique of transferring print data to the set-top box via a network only after confirming that the concerned communication channel is a secured one. This technique ensures the integrity of print data between the print data transfer source and the set-top box.
At the same time, it is required to maintain a certain degree of freedom in the network configuration so as to cope with various user environments and user requests. In light of this, the system should allow the selection of either a configuration in which a control device and a printer having a function for decrypting encrypted data are directly connected by a cable, or a configuration in which they are connected via a network such as a LAN.
When a printer does not include any function for decrypting encrypted data, unencrypted data shall be transferred from the control device to the printer by directly connecting the control device and printer with a cable. This direct connection prevents any leakage of confidential information that could otherwise occur in a network configuration. Even when a printer has a function for decrypting encrypted data, the processing load of data encryption and decryption may be reduced by directly connecting the control device and the printer with a cable.
On the other hand, when a control device and a printer are connected via a network, the integrity of the transmitted print data must be ensured differently. Japanese Patent Laid-Open No. 2001-159960 described above assumes the configuration in which a printer and a set-top box serving as a control device are directly connected with a cable. Thus, Japanese Patent Laid-Open No. 2001-159960 does not consider the integrity of the transmitted print data between the set-top box and the printer when they are connected via a network.